1. Field of the Invention
The present invention relates to a gas turbine suction air filter, a gas turbine using this filter and a method for using this filter.
2. Description of the Prior Art
A gas turbine generally comprises an air suction portion, a compressor, a combustor and a turbine portion. Air is taken from the air suction portion and is supplied into the compressor to be compressed. The compressed air is sent to the combustor. In the combustor, the compressed air and fuel are mixed together to be burned continuously. By the combustion, a high temperature, high pressure combustion gas is generated to be supplied into the turbine portion. By expansion of the combustion gas, moving blades of the turbine portion are driven to rotate a rotor and thereby to generate an electric power.
If foreign matters, such as dust, is included in the air to be supplied into the compressor, the foreign matters attaches to the blades of the compressor to thereby reduce the compression efficiency. Thus, in order to remove the foreign matters, the air is filtered at the air suction portion. Usually, the air suction portion is provided with a first filter portion, which is constructed by a multiplicity of juxtaposed coarse dust filters, a second filter potion, which is constructed by a multiplicity of juxtaposed medium and high performance filters, and a third filter portion which is constructed by a multiplicity of juxtaposed ultra-high performance filters. With these filter portions, dust is removed. It is to be noted that, in some gas turbines, the third filter portion is ommitted.
As clogging occurs in each of the filters after long term use, the filter must be replaced. It is the present situation that the coarse dust filter is replaced at an interval of about three months, the medium and high performance filter at an interval of about 6 to 12 months and the ultra-high performance filter at an interval of about 12 months. The filter, after use, is disposed as industrial waste.
As the gas turbine consumes a large volume of air, a multiplicity of filters are needed. For example, in a usual gas turbine, the first filter portion, the second filter portion and the third filter portion, have some hundreds of filters therein, and each of the filters has an opening area of about 0.35 m2. Therefore, in every case of the replacement, a large quantity of industrial waste is discharged. This causes a problem from the viewpoint of the environment preservation. Also, it is not preferable, from the point of view of resource savings, to use such a large quantity of filters This invites an increase in the running cost of the gas turbine.
In view of the above mentioned problems, trials are been done recently to wash the filter after used for reuse thereof. For the washing, an ultrasonic washer is most appropriate. In the ultrasonic washer, cavitations are generated by an ultrasonic wave. When these cavitations disappear, impulse forces are generated and the dust attached to the filter cloth is thereby removed.
FIG. 5 is a partial cross sectional view of one prior art example of a medium and high performance filter 51 which is used in the air suction portion. In FIG. 5, air comes from the direction of arrow A and passes through the filter 51. The filter 51 comprises a multiplicity of separators 53 which are made of aluminum or the like. Each of the separators 53 is formed in a corrugated shape and extends perpendicularly to the plane of FIG. 5. A filter cloth 55, which is made of a glass fiber non-woven fabric or the like, is provided between each of the separators 53. The filter cloth 55 is arranged in a serpentine form so as to alternately pass right hand ends and left hand ends of the separator 53. By this arrangement, area of the filter cloth 55, which is also an air passing area, becomes larger and the dust collection efficiency is enhanced.
As the gas turbine consumes a large volume of air, as described above, the multiplicity of filters 51 are used in the air suction portion. For this reason, the air suction portion becomes extremely large. Thus, the gas turbine needs a wide installation space and construction costs becomes high. In order to mitigate this problem, in the filter 51 for the gas turbine, as compared with general filters, such as those for air conditioning in a building, a pitch P, as shown in FIG. 5, between each of the separators 53 is made smaller. Hence, the air passing area becomes large, the number of filters 51 to be used for the air suction portion is reduced, and a smaller size of the air suction portion is thereby attained.
For example, while the separator pitch in the general filter is 10 to 15 mm, the separator pitch P in the filter 51 for the gas turbine air suction portion is about 5 mm. By this arrangement, while the capacity, or the air passing volume per filter, of the general filter is 35 to 50 m3/minute, that of the gas turbine air suction portion attained is as high as about 50 to 70 m3/minute.
However, even though the filter 51 in which the separator pitch P is made smaller is washed by an ultrasonic washer, transmission of the ultrasonic wave is obstructed by the separator 53, so that the ultrasonic wave hardly reaches the entire portion of the filter cloth 55, and there is a problem in that the dust is not sufficiently removed. This problem makes the reuse of the filter 51 for the gas turbine air suction portion difficult as compared with a general filter.
Also, as mentioned above, the prior art filter 51 for use in the gas turbine suction air portion, after use, is disposed as industrial waste, not to be reused. This increases the running cost of the gas turbine having the air suction portion mounted with the filter 51.
In view of the mentioned problems in the prior art, it is an object of the present invention to provide a gas turbine suction air filter and a method for using the same by which a large capacity is realized and dust can be still be easily removed by an ultrasonic washer. Also, it is another object of the present invention to provide a gas turbine in which the filter of the present invention is used.
In order to achieve the mentioned objects, the present invention provides a gas turbine suction air filter comprising a frame member having an air passing cross section formed in a rectangular shape and a filter cloth contained in the frame member. The filter cloth is folded so that a multiplicity of folded faces may be formed along an air passing direction and adjacent ones of the folded faces directly confront each other with only a space being arranged therebetween.
In the mentioned filter, as the filter cloth is folded so that the multiplicity of the folded faces may be formed along the air passing direction, the air passing area is large and hence the capacity is large. Also, in this filter, as the adjacent ones of the folded faces directly confront each other with only a space being arranged between them, and no intervening member, such as a separator, is provided between adjacent ones of the folded faces, the ultrasonic wave reaches to the entire filter cloth. Thus, sufficient dust removal can be attained by the ultrasonic washer.
It is preferable that the frame member constituting the mentioned filter of the present invention is made of a metal material.
In the metal material, the ultrasonic wave transmission is damped less. Also, as the metal material is excellent in the strength and rigidity, the thickness of the frame member can be made smaller as compared with a frame member constructed of a wooden material, a synthetic resin or the like. That is, in the frame member of the filter of the present invention, less damping of the ultrasonic wave is effected not only for the reason of the material, but also because of the thickness of the member. Thus, in this filter, even though the air passing area is large, the ultrasonic wave easily reaches to the entire filter cloth. This metal frame member is appropriate for use in the filter of a large capacity, or more concretely of a capacity (air volume passing through an opening area of 0.35 m2) of 50 m3/minute or more.
The frame member is preferably constructed of a stainless steel which effects less damping of the ultrasonic wave, is excellent in the strength and rigidity, and is also excellent in corrosion resistance.
The filter cloth is preferably made of a non-woven fabric including a synthetic resin fiber. As compared with glass fiber, synthetic resin fiber is more flexible and the fibers are entangled more densely. Thus, there is no need to use a binder for adhesion of the fibers as used in the glass fiber non-woven fabric. Also, there is no case where the binder dissolves into the wash liquid to loosen the fibers, as in the case of the glass fiber non-woven fabric. The filter cloth may be constructed of a combination of synthetic resin fiber and the glass fiber, but even in such case it is preferable that the ratio of the synthetic resin fiber to the entireity of the fibers is 50% or more in volume.
The synthetic resin fiber is preferably a polypropylene or polyester fiber, as it is produced on a large scale so as to be less expensive and generates no poisonous gas when it is burned for disposal.
Further, in place of the synthetic resin fiber, a porous sheet made of a synthetic resin may be used. The porous sheet made of the synthetic resin has numerous minute pores for passing air and uses no fiber. Hence, occurs no loosening of the fiber occurs. In the porous sheet of synthetic resin, there is a need to form numerous minute air holes for securing a filter performance and, in view of strength and the manufacturing process, it is preferable to use a polytetrafluoroethylene resin as a base material.
Also, in order to achieve the above mentioned objects, the present invention provides a gas turbine suction air filter comprising a frame member formed in a cylindrical shape and having an air passing portion at a cylinder portion of the cylindrical shape. A filter cloth is formed in a cylindrical shape and is contained in the frame member. The filter cloth is a non-woven fabric including a synthetic resin fiber.
In the filter so constructed, air to be filtered can flow uniformly in the entire filter cloth through the air passing portion of the frame member formed in the cylindrical shape. Also, in addition to washing by ultrasonic wave, a pulse type air wash can be combined and a sufficient dust removal can be performed.
Further, the filter cloth is constructed of a non-woven fabric including a synthetic resin fiber, whereby the ultrasonic wash can be done repeatedly in the wash liquid. In this case, the ratio of the synthetic resin fiber to the entire fibers is preferable to be 50% or more in volume.
The synthetic resin fiber is preferably a polypropylene or polyester fiber, as it can be produced on a large scale so as to be less expensive, and generates no poisonous gas when it is burned for disposal.
A gas turbine mounted with the above mentioned filter of the present invention can contribute to resource savings and environment preservation. Also, in this gas turbine, the running cost is reduced, as the filter can be washed by the ultrasonic washer so as to be reused.